Linear alpha olefins (LAOs) are olefins with a chemical formula CxH2x, distinguished from other mono-olefins with a similar molecular formula by linearity of the hydrocarbon chain and the position of the double bond at the primary or alpha position. Linear alpha olefins comprise a class of industrially important alpha-olefins, including 1-butene, 1-hexene, 1-octene, 1-decene, 1-dodecene, 1-tetradecene, 1-hexadecene, 1-octadecene and higher blends of C20-C24, C24-C30, and C20-C30 olefins. Linear alpha olefins are very useful intermediates for the manufacture of detergents, synthetic lubricants, copolymers, plasticizers, and many other important products. Existing processes for the production of linear alpha olefins typically rely on the oligomerization of ethylene.
Linear alpha olefins can be prepared by the catalytic oligomerization of ethylene in the presence of a Ziegler-Natta-type catalyst. Important considerations of the ethylene oligomerization are the desired selectivity and the desired product distribution. The applied catalyst and the process conditions are essential features to obtain the desired characteristics. Various types of catalysts have been applied in the process for the oligomerization of ethylene, including titanium and zirconium-containing catalyst systems. The main disadvantages of such catalysts include poor solubility, harsh operating conditions, and low catalyst selectivity. During the oligomerization process there can be significant amounts of undesirable wax and polymer formation in the presence of these catalysts.
An intrinsic problem of all of these metal-catalyzed ethylene oligomerization processes is the production of linear alpha olefin mixtures of chain length 4, 6, 8, and so on, which can be difficult to separate and whose composition often does not match market demands. This is due to a chemical mechanism which is widely governed by competing chain growth and displacement reaction steps, leading to a Schulz-Flory or Poisson product distribution.
There is an active interest to overcome the above-described technical limitations, to transform the non-selective ethylene oligomerization reactions into more selective processes, and to provide oligomerization catalysts having increased catalytic activity. Accordingly, there remains a need for an improved process for the oligomerization of ethylene to produce linear alpha olefins having improved linearity to meet increased market demands.